Stereotaxic radiosurgery makes it possible to deliver an ablative dose of ionizing radiation with high precision to brain tumors while minimizing damage to surrounding normal tissue. Funding is being sought to develop a prototype system which utilizes novel technology to dramatically expand the applications of this technique. The surgery, are; 1) its reliance on novel computerized method for target localizations and control rather than conventional stereotaxic frames 2) the utilization of an ultra low weight commercially available 6 MeV linear accelerator currently being used only for industrial radiography. This technology will significantly improve treatment for the many brain tumors which are either inaccessible or poorly accessible by conventional neurosurgical techniques. Most importantly, this system will make fractionated treatments practical, and as consequence, a new type of therapy with ionizing radiation; one that blends conventional radiation therapy techniques with neurosurgical principles of anatomic localization. In addition to improving patient care, several aspects of this technology have considerable potential for commercial development.